Keys To Summer Plant Growth Regulator Success

Keys To Summer Plant Growth Regulator Success

The switch from spring crops to summer crops can be a challenge for growers because of increased day length and day/night temperatures. Plants grown during long days and in warm temperatures with a robust fertility program will exhibit the following: good growth and more good growth. Warm summer evenings will generally add to stem elongation on most plants. PGRs (plant growth regulators) can play a key role in reducing unwanted stretch and can help carry-over crop inventory if the weather slows sales down for a period of time.

A good example would be late spring production of violas or pansies. As the weather warms up, violas can stretch and get rather loose in growth. You may find the normal rate of 2-3 PPM Paczol® (paclobutrazol) sprayed is not enough to control stretch and you may need to increase the rate to 3-5 PPM or higher depending on conditions. Using one-half the normal PGR rates on crops is a good tool for holding plants over for a short period of time. You could use this technique during slow sales periods or excess inventory.


A tip to remember — if your crop is mostly leaves (few stems exposed) then PGRs like B-Nine® or Cycocel® are best. Both are absorbed thoroughly through leaves. If the crop has smaller leaves and good stem exposure, then Paczol should be considered. Paczol is not leaf absorbed; it is absorbed through stems and roots. If your crop is a real challenge to control, using Paczol as a drench is a very effective tool. Paczol spray-to-drench rates are a 10 to 1 factor–i.e. a 10 PPM Paczol spray is roughly the same as a 1 PPM Paczol drench.

While you’re growing your summer crops, you may want to begin planning out your fall crops such as mums and poinsettias. Mums and poinsettias respond well to BNine or Cycocel applications. A late season drench application of Paczol is a proven method to control late season stretch (early November, depending on your climate) of poinsettia crops.

These and other methods can help you manage plant growth and produce a great crop. For more information, visit our website at